1. Field of the Invention
The present invention relates to a resonant power conversion apparatus applicable to, for example, a hybrid vehicle inverter and an electric vehicle inverter.
2. Description of the Related Art
Among power conversion apparatuses, the resonant power conversion apparatus is known to be capable of reducing a switching loss. A typical example of the resonant power conversion apparatus is an auxiliary resonant commutated pole three-phase voltage inverter that reduces a switching loss by soft-switching switches through an auxiliary resonant circuit that performs resonant operation.
FIG. 1 is a circuit diagram illustrating a one-phase portion of an auxiliary resonant commutated pole three-phase voltage inverter according to a related art disclosed in Japanese Unexamined Patent Application Publication No. H08-340676. In FIG. 1, both ends of a DC power source Vdc are connected to a series circuit including capacitors C1 and C2 having the same capacitance. A connection point of the capacitors C1 and C2 generates a voltage that is half a voltage of the DC power source Vdc.
Switches S1 and S2 are insulated gate bipolar transistors (IGBTs) and are connected in series. Both ends of the series circuit of the switches S1 and S2 are connected to the ends of the DC power source Vdc. The switch S1 has a collector and an emitter between which a capacitor Cr1 and a diode D1 are connected. The switch S2 has a collector and an emitter between which a capacitor Cr2 and a diode D2 are connected. A connection point of the switches S1 and S2 is connected to a load RL.
Connected between the connection point of the switches S1 and S2 and the connection point of the capacitors C1 and C2 is a series circuit including a reactor Lr and switches Sa1 and Sa2. The switches S1a and Sa2 form an auxiliary resonant circuit and are connected to diodes Da1 and Da2, respectively.
The switches S1 and S2 carry out a zero-voltage, zero-current turn-ON operation with a resonant current provided by the auxiliary resonant circuit, to greatly reduce a switching loss.
FIG. 2 is a timing chart illustrating operating waveforms of the switches in the auxiliary resonant commutated pole three-phase voltage inverter illustrated in FIG. 1. FIG. 3A is a mode transition diagram of the inverter illustrated in FIG. 1 from mode M0 of state A to mode M2 of state A. FIG. 3B is a mode transition diagram of the same from mode M3-1 of state A to mode M3 of state B.
In FIG. 2, S1g is a gate signal applied to a gate of the switch S1, S2g is a gate signal applied to a gate of the switch S2, Sa1g is a gate signal applied to a gate of the switch Sa1, and Sa2g is a gate signal applied to a gate of the switch Sa2.
Operation of the resonant power conversion apparatus of FIG. 1 will be explained with reference to FIGS. 2 to 3B. In mode M0 of state A, the switch S1 is ON and the diode D1 turns on to pass a current through a path extending along the load RL, the diode D1, and the DC power source Vdc.
In mode M1-1 of state A, the gate signal Sa1g turns on the switch Sa1 to divide a current from the load RL. A divided current portion passes through the diode D1 to the DC power source Vdc and the other divided current portion passes through the reactor Lr, diode Da2, and switch Sa1, to accumulate power in the reactor Lr.
In mode M1-2 of state A, a current of the switch S1 and a current of the load RL (each arrowed) pass through the reactor Lr, diode Da2, and switch Sa1, to accumulate power in the reactor Lr.
In mode M2 of state A, the gate signal S1g turns off the switch S1 and the reactor Lr and capacitors Cr1 and Cr2 resonate. At this time, the capacitor Cr2 connected in parallel with the switch S2 is discharged and the capacitor Cr1 connected in parallel with the switch S1 is charged.
In modes M3-1 and M3-2 of state A, the capacitor Cr2 completes the discharge and the diode D2 passes a current. When a drain-source voltage of the switch S2 is zero, the gate signal S2g turns on the switch S2, to realize the zero-voltage switching of the switch S2.
In mode M0 of state B, a current from the load RL passes through the switch S2. In mode M1 of state B, the gate signal Sa2g turns on the switch Sa2, so that a current passing through a path extending along Da1, Sa2, and Lr from the left to the right together with a current of the load RL pass through the switch S2.
In mode M2 of state B, the gate signal S2g turns off the switch S2. Then, the reactor Lr and capacitors Cr1 and Cr2 resonate. At this time, the capacitor Cr1 connected in parallel with the switch S1 is discharged and the capacitor Cr2 connected in parallel with the switch S2 is charged.
In mode M3 of state B, the capacitor Cr1 completes the discharge and the diode D1 passes a current. When a drain-source voltage of the switch 51 is zero, the switch S1 is turned on, to realize the zero-voltage switching of the switch S1.